Epoxy resin advanced with polyphenol/oxyalkylated aromatic or cycloyaliphatic diglycidyl ether product

ABSTRACT

Advanced epoxy resin compositions are prepared by reacting a composition comprising (1) an aromatic hydroxyl-containing product resulting from reacting a composition comprising (a) at least one diglycidyl ether of (i) an oxyalkylated aromatic diol, or (ii) at least one compound having two hydroxyl groups per molecule in which the hydroxyl groups are attached to an aliphatic or cycloaliphatic carbon atom and which compound is free of aromatic rings; or (iii) a combination of (i) and (ii); and (iv) optionally a diglycidyl ether compound different from (i) and (ii); and (b) at least one compound containing two aromatic hydroxyl groups per molecule; (2) at least one diglycidyl ether of a compound containing two aromatic groups per molecule; (3) optionally, one or more compounds containing two aromatic hydroxyl groups per molecule; and (4) optionally, a monofunctional capping agent. The advanced resins are useful in coating compositions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of application Ser. No. 08/015,505 filedFeb. 9, 1993 (now U.S. Pat. No. 5,276,071) which is a division ofapplication Ser. No. 07/516,018 filed Apr. 27, 1990 (now U.S. Pat. No.5,212,262) which is a continuation-in-part of application Ser. No.07/372 064 filed Jun. 27, 1989 (now abandoned) which is a division ofapplication Ser. No. 07/128,249 filed Dec. 3, 1987 (now U.S. Pat. No.4,863,575) which claims a priority date of Jul. 16, 1987 (WO) PCTInternational Application PCT/US87/01690 all of which are incorporatedherein by reference in their entirety.

FIELD OF THE INVENTION

The invention is concerned with advanced epoxy resin compositions, amethod for their preparation and the use of such compositions incathodic electrodeposition.

BACKGROUND OF THE INVENTION

Electrodeposition has become an important method for the application ofcoatings over the last two decades and continues to grow in popularitybecause of its efficiency, uniformity and environmental acceptance.Cathodic electrodeposition has become dominant in areas where highlycorrosion-resistant coatings are required, such as in primers forautomobile bodies and parts. Epoxy based systems provide the bestoverall performance in this application and are widely used.

Cathodic electrodeposition resins based on conventional epoxies obtainedby reacting liquid diglycidyl ethers of bisphenol A with bisphenol A toproduce higher molecular weight epoxy resins have known disadvantages.Such products tend to have excessively high softening points resultingin poor flow out. In addition, such products require excessive amountsof solvent during their preparation. In order to improve flow, it hasbeen proposed to modify such conventional epoxy resins by reaction witha diol in the presence of a tertiary amine catalyst. Thus, Bosso et al.,U.S. Pat. No. 3,839,252, describes modification with polypropyleneglycol. Marchetti et al., U.S. Pat. No. 3,947,339, teaches modificationwith polyester diols or polytetramethylene glycols. Wismer et al., U.S.Pat. No. 4,419,467, describes still another modification with diolsderived from cyclic polyols reacted with ethylene oxide. These variousmodifications, however, also have disadvantages. Tertiary amines orstrong bases are required to effect the reaction between the primaryalcohols and the epoxy groups involved. Since these reactions requirelong cook times, they are subject to gellation because of competitivepolymerization of the epoxy groups by the base catalyst. In additionepoxy resins containing low levels of chlorine are required to preventdeactivation of this catalyst.

U.S. Pat. Nos. 4,419,467 and 4,575,523 describe the reaction of an epoxyresin with oxyalkylated diols to form resins useful inelectrodeposition. Such reactions have several attendant disadvantages,such as described in U.S. Pat. No. 4,260,720, col. 1, lines 25-51. Useof the glycidyl ethers of such a diol, as described herein, eliminatesor greatly reduces these problems.

U.S. Pat. No. 4,260,720 teaches the use of glycidyl ethers of cyclicpolyols, including oxyalkylated polyphenols, in combination withpolymercapto compounds to form electrodeposition resins. These glycidylethers were not used in combination with glycidyl ethers of polyphenolsand polyphenols, as described herein, nor were there advantageousproperties as modifiers for bisphenol A-based epoxy resins inelectrodeposition anticipated, such as improvement in film thickness andappearance.

U.S. Pat. No. 4,698,141 issued Oct. 6, 1987 to Anderson and Hicknerdiscloses an improvement in a method for preparing an advanced epoxycationic resin from an epoxy-based resin containing oxirane groups byconverting at least some of the oxirane groups to cationic groups. Theimprovement is stated to reside in using as the epoxy-based resin anadvanced epoxy resin obtained by reacting in the presence of a suitablecatalyst (1) a diglycidyl ether of a polyether polyol such as thecondensation product of dipropylene glycol and epichlorohydrin having anepoxy equivalent weight of 185, (2) a diglycidyl ether of a dihydricphenol such as a diglycidyl ether of bisphenol A and (3) a dihydricphenol such as bisphenol A and optionally a capping agent such asp-nonylphenol.

U.S. Pat. No. 4,868,230 issued Sep. 19, 1989 to Rao and Hicknerdiscloses an improvement in a method for preparing an advanced epoxycationic resin from an epoxy-based resin containing oxirane groups byconverting at least some of the oxirane groups to cationic groups. Theimprovement is stated to reside in using as the epoxy-based resin anadvanced epoxy resin obtained by reacting in the presence of a suitablecatalyst (1) a diglycidyl ether of an aliphatic diol which isessentially free of ether oxygen atoms, such as a diglycidyl ether of1,4-butanediol,(2) a diglycidyl ether of a dihydric phenol such as adiglycidyl ether of bisphenol A and (3) a dihydric phenol such asbisphenol A and optionally a capping agent such as p-nonylphenol.

Many coating formulations applied by electrodeposition include pigmentsto provide color, or opacity or application or film properties. U.S.Pat. No. 3,936,405, Sturni et al., describes pigment grinding vehiclesespecially useful in preparing stable, aqueous pigment dispersions forwater-dispersible coating systems, particularly for application byelectrodeposition. The final electrodepositable compositions, asdescribed, contain the pigment dispersion and an ammonium or amine saltgroup solubilized cationic electrodepositable epoxy-containing vehicleresin and other ingredients typically used in electrodepositablecompositions. Among the kinds of resins used are various polyepoxidessuch as polyglycidyl ethers of polyphenols, polyglycidyl ethers ofpolyhydric alcohols and polyepoxides having oxyalkylene groups in theepoxy molecule.

The automobile industry still has needs in the areas of controlled filmthickness and lower temperature cure systems. The ability to buildthicker, uniform films which are smooth and free of defects will allowthe elimination of an intermediate layer of paint known as a primersurface or spray primer, previously required to yield a sufficientlysmooth surface for the topcoat. Such an elimination results in removalof one paint cycle and provides more efficient operations.

European Patent Application 0,253,405 published Jan. 20, 1988 disclosescationic resins prepared from an advanced epoxy resin prepared in onestep by reacting in the presence of a suitable catalyst, (A) acomposition comprising (1) at least one diglycidyl ether of a polyol and(2) at least one diglycidyl ether of a dihydric phenol with (B) at leastone dihydric phenol and (C) optionally, a monofunctional capping agent.

The cationic advanced epoxy resins prepared by the procedure of theEuropean Patent Application 0,253,405 satisfies many of the requirementsdesired by the automobile industry. Nevertheless, it would be desired tohave available cationic resins which provide further improvements incoating properties such as higher rupture voltage, lower bathconductivity, and the attendant improvement in appearance at highercoating voltages, and the like. Thicker electrocoat primers may alsoprovide improved corrosion resistance.

SUMMARY OF THE INVENTION

The present invention pertains to an advanced epoxy resin compositioncomprising the product resulting from reacting a composition comprising

(1) the aromatic hydroxyl-containing product resulting from reacting acomposition comprising

(a) at least one diglycidyl ether of (i) an oxyalkylated aromatic diol,or (ii) at least one compound having two hydroxyl groups per molecule inwhich the hydroxyl groups are attached to an aliphatic or cycloaliphaticcarbon atom and which compound is free of aromatic rings; and (iii)optionally, a diglycidyl ether compound different from (i) and (ii)which is present in an amount such that the amount of epoxy groupscontributed by component (iii) based upon the total amount of epoxygroups contributed by components (i), (ii) and (iii) is from about zeroto about 75 percent; and

(b) at least one compound containing two aromatic hydroxyl groups permolecule; wherein components (a) and (b) are employed in amounts suchthat there are more aromatic hydroxyl groups present than glycidyl ethergroups;

(2) at least one diglycidyl ether of a compound containing two aromatichydroxyl groups per molecule;

(3) optionally, one or more compounds containing two aromatic hydroxylgroups per molecule; and

(4) optionally, a monofunctional capping agent;

wherein components (1) and (2) are employed in amounts such that theresultant product has an epoxide equivalent weight greater than that ofcomponent (2); component (3), when present, is employed in an amountwhich provides a total amount of aromatic hydroxyl groups fromcomponents (1) and (3) per epoxide group contained in component (2) offrom about 0.5:1 to about 0.95:1; and component (4), when present, isemployed in an amount which provides a ratio of epoxy-reactive groupscontained in component (4) per glycidyl group not consumed by reactionof components (1) and (3) with component (2) suitably from about zero: 1to about 0.7:1, more suitably from about 0.1:1 to about 0.7:1, mostsuitably from about 0.2:1 to about 0.5:1.

The present invention also pertains to a composition comprising amixture of

(A) an advanced epoxy resin resulting from reacting a compositioncomprising

(1) the aromatic hydroxyl-containing product resulting from reacting acomposition comprising

(a) at least one diglycidyl ether of (i) an oxyalkylated aromatic diol,or (ii) at least one compound having two hydroxyl groups per molecule inwhich the hydroxyl groups are attached to an aliphatic or cycloaliphaticcarbon atom and which compound is free of aromatic rings; and (iii)optionally, a diglycidyl ether compound different from (i) and (ii)which is present in an amount such that the amount of epoxy groupscontributed by component (iii) based upon the total amount of epoxygroups contributed by components (i), (ii) and (iii) is from about zeroto about 75 percent; and

(b) at least one compound containing two aromatic hydroxyl groups permolecule; wherein components (a) and (b) are employed in amounts suchthat there are more aromatic hydroxyl groups present than glycidyl ethergroups;

(2) at least one diglycidyl ether of a compound containing two aromatichydroxyl groups per molecule;

(3) optionally, one or more compounds containing two aromatic hydroxylgroups per molecule; and

(4) optionally, a monofunctional capping agent; and

(B) at least one diglycidyl ether of a compound having two aromatichydroxyl groups per molecule; and

wherein components (A1) and (A2) are employed in amounts such that theresultant product has an epoxide equivalent weight greater than that ofcomponent (A2); component (A3) is present in an amount of from aboutzero to about 25 percent by weight based on the total weight ofcomponents (1), (2) and (3); and component (A4), if present, is employedin an amount of from about zero to about 15 percent by weight based onthe total weight of components (1), (2), (3) and (4); and components (A)and (B) are present in an amount such that from about 25 to about 95percent of the total amount of glycidyl ether groups are contributed bycomponent (A) and from about 5 to about 75 percent of the total amountof glycidyl ether groups are contributed by component (B).

Another aspect of the present invention pertains to cationic resinsobtained by reacting the aforementioned resins with a nucleophiliccompound and adding an organic acid and water at at least one pointduring the preparation of the cationic resin.

The present invention further pertains to a coating compositioncomprising aqueous dispersions of the above-described cationic resins.

The present invention further pertains to curable compositionscomprising the aforementioned epoxy resin compositions and at least onesuitable curing agent therefor.

The present invention also pertains to articles resulting from curingthe aforementioned curable compositions.

The present invention makes possible the preparation of cationic resinswhich provide improvements in one or more coating properties such as animprovement in one or more of the properties of electrodepositablecoatings including higher rupture voltage, lower bath conductivity, andthe attendant improvement in appearance at higher coating voltages, andthe like. Also, thicker electrocoat primers may also provide improvedcorrosion resistance.

DETAILED DESCRIPTION OF THE INVENTION

The aromatic hydroxyl-containing compound, component (1) is prepared byreacting a composition comprising (a) at least one diglycidyl ether of(i) an oxyalkylated aromatic diol, or (ii) at least one compound havingtwo hydroxyl groups per molecule in which the hydroxyl groups areattached to an aliphatic carbon atom and which compound is free ofaromatic rings, and (iii), optionally, a diglycidyl ether compounddifferent from (i) and (ii) which is present in an amount such that theamount of epoxy groups contributed by component (iii) based upon thetotal amount of epoxy groups contributed by components (i), (ii) and(iii) is suitably from about zero to about 75, percent, more suitablyfrom about zero to about 50, most suitably from about zero to about 30percent; (b) at least one compound containing two aromatic hydroxylgroups per molecule; and (c) optionally, at least one diglycidyl etherof a compound containing two aromatic hydroxyl groups per molecule.

The aromatic hydroxyl-containing compound is usually prepared byconducting the reaction at a temperature in the range of from about 100°C. to about 220° C. preferably from about 125° C. to about 200° C., morepreferably from about 150° C. to about 180° C., for a time sufficient tosubstantially complete the reaction, suitably from about 5 minutes toabout 2 hours, more suitably from about 10 minutes to about 1 hour, mostsuitably from about 15 minutes to about 45 minutes, in the presence of asuitable catalyst. The reaction can, optionally, be conducted in anappropriate solvent to reduce the viscosity, facilitate mixing andhandling, and assist in controlling the heat of reaction.

Many useful catalysts for the desired reactions are known in the art.Examples of suitable catalysts include ethyltriphenylphosphoniumacetate.acetic acid complex; ethyltriphenylphosphonium chloride,bromide, iodide, or phosphate; and tetrabutylphosphonium acetate.aceticacid complex. The catalysts are typically used at levels of from about0.0001 to about 0.05 mole of catalyst per epoxide group.

Appropriate solvents include aromatic solvents, glycol ethers, glycolether esters, high boiling esters or ketones, or mixtures. Other usefulsolvents will be apparent to those skilled in the art. Preferredsolvents are ethylene glycol monobutylether, xylene and propylene glycolmonophenylether. Solvent content can range from zero to 30 percent ofthe reaction mixture. A solvent is usually chosen which is compatiblewith the subsequent cation-forming reactions and with the final coatingcomposition so that the solvent does not require subsequent removal.

The components (1a) and (1b) are employed in amounts such that there aremore aromatic hydroxyl groups present than glycidyl ether (epoxy)groups, suitably in amounts which provide a ratio of aromatic hydroxylgroups per glycidyl ether group of from about 1.05:1 to about 10:1, moresuitably from about 1.1:1 to about 7.5:1, most suitably from about 1.2:1to about 6:1. These ratios are dependent upon the level of component(1a) in the total reaction mixture and the epoxide equivalent weightdesired of the final product, as well as the amount of components (3)and (4) employed, if any.

The advanced epoxy resin composition is prepared by reacting acomposition comprising a mixture of (1) the aforementioned aromatichydroxyl-containing compound; (2) at least one diglycidyl ether of acompound containing two aromatic hydroxyl groups per molecule; (3)optionally, one or more compounds containing two aromatic hydroxylgroups per molecule; and (4) optionally, a monofunctional capping agent.

The aromatic hydroxyl-containing compound, component (1) and thediglycidyl ether of a compound containing two aromatic hydroxyl groupsper molecule, component (2), are employed such that the resultantproduct contains an epoxide equivalent weight (EEW) greater than that ofcomponent (2), usually in an amount such that the ratio of aromatichydroxyl groups per epoxide (glycidyl ether) group is suitably fromabout 0.01:1 to about 0.95:1, more suitably from about 0.05:1 to about0.9:1, most suitably from about 0.08:1 to about 0.8:1.

The optional compound containing two aromatic hydroxyl groups, component(3), is employed in an amount which provides the final advanced epoxyresin product with the desired epoxide equivalent weight (EEW).Typically, this amount is that which provides, when added to thearomatic hydroxyl groups provided by component (1), a total ratio ofaromatic hydroxyl groups per glycidyl ether group of suitably from about0.5:1 to about 0.95:1, more suitably from about 0.5:1 to about 0.9:1,most suitably from about 0.55:1 to about 0.8:1.

The optional monofunctional capping agent, component (4), is employed inan amount suitably from about zero to about 15, more suitably from about1 to about 15, most suitably from about 2 to about 10 percent by weightbased on the total weight of components (1), (2), (3) and (4).

The optional monofunctional capping agent, component (4), isalternatively employed in an amount which provides a ratio ofepoxy-reactive groups contained in component (4) per glycidyl group notconsumed by reaction of components (1) and (3) with component (2)suitably from about zero: 1 to about 0.7:1, more suitably from about0.1:1 to about 0.7:1, most suitably from about 0.2:1 to about 0.5:1.

Glycidyl ethers of dihydric phenols (glycidyl ethers of compoundscontaining an average of about two aromatic hydroxyl groups permolecule) useful for the preparation of these resins are those having anaverage of more than one, preferably an average of two, vicinal epoxidegroups per molecule. These polyepoxides can be produced by condensationof an epihalohydrin with a dihydric phenol in the presence of abasic-acting substance, such as an alkali metal hydroxide.

Particularly useful such glycidyl ethers of dihydric phenols arerepresented by Formulas I and II: ##STR1## wherein A is a divalenthydrocarbon group having suitably from 1 to 12, more suitably 1 to 6,carbon atoms, --S--, --S--S--, --SO₂ --, --SO--, --CO--, --O--CO--O--,or --O--; each R is independently hydrogen or a hydrocarbyl group havingfrom 1 to 4 carbon atoms; each R' is independently hydrogen, ahydrocarbyl or hydrocarbyloxy group having from 1 to 4 carbon atoms, ora halogen, preferably chlorine or bromine; n has a value of zero or 1;and n' has a value suitably from zero to 10, more suitably from 0.1 to5.

The term hydrocarbyl as employed herein means any aliphatic,cycloaliphatic, aromatic, aryl substituted aliphatic or cycloaliphatic,or aliphatic or cycloaliphatic substituted aromatic groups. Thealiphatic and cycloaliphatic groups can be saturated or unsaturated.Likewise, the term hydrocarbyloxy means a hydrocarbyl group having anoxygen linkage between it and the carbon atom to which it is attached.

The preferred polyglycidyl ethers of dihydric phenols (compounds havingtwo aromatic hydroxyl groups per molecule) are the diglycidyl ether ofbisphenol A and the oligomeric glycidyl ethers of bisphenol A.

Suitable dihydric phenols which can be employed herein to prepare theaforementioned polyepoxides include, for example, those represented bythe following Formulas III or IV ##STR2## wherein A, R, R', n and n areas defined above.

Particularly suitable dihydric phenols useful for the production ofthese polyepoxides include 2,2-bis(4-hydroxyphenyl)-propane (bisphenolA), 1,1-bis(2-hydroxyphenyl)-1-phenylethane (bisphenol AP),1,1-bis(4-hydroxyphenyl)ethane, bis(4-hydroxyphenyl)methane (bisphenolF), p,p'-hydroxybiphenyl, resorcinol, catechol, hydroquinone, or thelike.

The diglycidyl ethers of oxyalkylated aromatic diols (component 1ai)useful in the preparation of the advanced epoxy resins of the presentinvention are those which can be represented by the following Formula V:##STR3## wherein R is as hereinbefore defined; R" is hydrogen, an alkylgroup having suitably from 1 to 6, more suitably from 1 to 4, carbonatoms or a hydrocarbyl, or a hydrocarbyloxy group having from 1 to about4 carbon atoms; each m is independently an integer suitably from 1 to25, more suitably from 1 to 15, most suitably from 1 to 10; and Z is adivalent aromatic group having suitably from 6 to 20, more suitably from6 to 15, carbon atoms or Z is a group represented by the followingFormulas A, B, C or D: ##STR4## wherein A, R, R', n, and n' are definedas hereinbefore; each R^(a) is independently a divalent hydrocarbongroup having from 1 to about 6 carbon-atoms; and n" has a value of 1 or3.

The glycidyl ethers of the oxyalkylated aromatic diols are produced bythe condensation of an epihalohydrin with an oxyalkylated polyolrepresented by the following Formula VI: ##STR5## wherein R", Z, Z', n"and m are defined as hereinbefore. The resulting halohydrin product isthen dehydrohalogenated by known methods with a basic acting substance,such as sodium hydroxide to produce the corresponding diglycidyl ether.

The oxyalkylated diols of Formula VI are produced by reacting a diol ofthe following Formula VII

    HO--Z--OH                                                  (Formula VII)

wherein Z is defined as hereinbefore, with the appropriate molar ratioof ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran,styrene oxide or an alkyl or aryl glycidyl ether or mixtures thereof.Combinations of these oxides added in sequential manner can also be usedso as to form block copolymers rather than random polymers. Examples ofuseful aromatic diols include, hisphenol A, bisphenol F, hydroquinone,dihydroxydiphenyl oxide, resorcinol, p-xylenol and bisphenol cappedepoxy resin.

The diglycidyl ethers of compounds having two hydroxyl groups permolecule which hydroxyl groups (component 1aii) are attached to analiphatic or cycloaliphatic carbon atom and which compounds are free ofaromatic rings useful in the preparation of the resins of the presentinvention are-those which can be represented by the following FormulaVIII: ##STR6## wherein R is as hereinbefore defined; R" is hydrogen, analkyl group having suitably from 1 to 6, more suitably from 1 to 4,carbon atoms or a hydrocarbyl or hydrocarbyloxy group having from 1 toabout 4 carbon atoms; each m is independently an integer suitably fromzero to 25, more suitably from zero to 15, most suitably from zero to10; n" has a value of 1 or 3, y has a value of zero or 1 and Z' is adivalent aliphatic or cycloaliphatic group having suitably from 2 to 20,more suitably from 2 to 15, carbon atoms or Z' is a group represented bythe following Formulas A, B, C, D or E ##STR7## wherein R, R', R", n andn" are defined as hereinbefore; A' and R^(a) are divalent hydrocarbongroups having from 1 to about 6 carbon atoms; and R^(b) is hydrogen or ahydrocarbyl group having from 1 to about 6 carbon atoms; x has a valuesuitably from 2 to about 19, more suitably from about 3 to about 10,most suitably from about 3 to about 5.

The glycidyl ethers of these compounds having an average of about twohydroxyl groups per molecule which hydroxyl groups are attached to analiphatic or cycloaliphatic carbon atom and which compounds are free ofaromatic rings are produced by the condensation of an epihalohydrin witha diol represented by the following Formula IX: ##STR8## wherein R", Z',n" and m are defined as hereinbefore. The resulting halohydrin productis then dehydrohalogenated by known methods with a basic actingsubstance, such as sodium hydroxide to produce the correspondingdiglycidyl ether.

The oxyalkylated diols of Formula IX are produced by reacting a diol ofthe Formula X

    HO--Z'--OH (Formula X)

wherein Z' is defined as hereinbefore, with the appropriate molar ratioof ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran,styrene oxide, an alkyl or aryl glycidyl ether or mixtures thereof.Examples of useful diols include, 1,3-cyclohexanediol,1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, hydrogenated bisphenolA, hydrogenated bisphenol F, butanediol, hexanediol, ethylene glycol,propylene glycol, neopentyl glycol, or mixtures thereof.

Suitable compounds which can be employed as the optional component(1aiii) include any compound which is different from components (1ai)and/or (1aii). Such compounds include, for example, diglycidyl ethers ofcompounds having two aromatic hydroxyl groups per molecule. Particularlysuitable such compounds include those compounds described herein asbeing suitable for use as component (2). Particularly suitable suchcompounds include, for example, the diglycidyl ethers of bisphenol A,bisphenol AP, bisphenol F, combinations thereof and the like.

Some of the common methods of synthesis of the diglycidylethers ofoxyalkylated diols produce significant amounts of organicchloride-containing impurities. However, other processes are known forpreparing products with lower levels of such impurities. While thelow-chloride resins are not required for the practice of this invention,they can be used, if desired, for possible improvements in the processof preparing the resins, in the storage properties of the resins orformulated coatings made therefrom or in the performance properties ofthe products.

Compounds containing two aromatic hydroxyl groups per molecule useful ascomponents (1b) and component (3) are the same as those dihydric phenolsuseful for the production of the polyepoxides of component (2) ashereinbefore described. In practice, components (1b) and component (3)may be the same or different from each other and each may be the same ordifferent from the dihydric phenol from which component (2) is prepared.

The use of capping agents provides the advantageous ability to reducethe epoxide content of the resulting product without chain-extensionreactions and thus allows independent control of the average molecularweight and the epoxide content of the resulting resin within certainlimits. Use of a monofunctional compound to terminate a certain portionof the resin chain ends also reduces the average epoxy functionality ofthe reaction product. The monofunctional compound is typically used atlevels of zero to 0.7 equivalent of epoxy-reactive groups per equivalentof epoxy which would remain after reaction of substantially all of thearomatic hydroxyl groups of the compounds containing two aromatichydroxyl groups per molecule.

Examples of useful monofunctional capping agents are monofunctionalphenolic compounds such as phenol, tertiary-butyl phenol, cresol,para-nonyl phenol, higher alkyl substituted phenols; monofunctionalcarboxylic acids such as, for example, acetic acid, lactic acid, butyricacid, propionic acid or higher molecular weight mono acids; thiolcompounds such as, for example, dodecyl mercaptan; combinations thereofand the like. Preferred as the capping agent is para-nonyl phenol. Thetotal number of epoxy-reactive groups and the ratio of difunctional tomonofunctional phenolic compounds, if any are used, are chosen so thatthere will be a stoichiometric excess of epoxide groups. Ratios are alsochosen so that the resulting product will contain the desiredconcentration of terminal epoxy groups and the desired concentration ofresin chain ends terminated by the monofunctional compound aftersubstantially all of the epoxy-reactive groups are consumed by reactionwith epoxy groups. The capping agent is employed in an amount of fromzero to about 15, usually from about 1 to about 15, and more usuallyfrom about 2 to about 10 percent based on the total weight of the (1),(2), (3) and (4) components.

These amounts are dependent on the respective equivalent weights of thereactants and the relative amounts of the epoxy-functional componentsand can be calculated by methods known in the art. In the practice ofthis invention, the desired epoxide content of the reaction productuseful for preparation of the cationic resin is typically between about1 and about 8 percent, calculated as the weight percentage of oxiranegroups, and preferably is from about 2 to about 6 percent and is mostpreferably from about 2 to about 4 percent. These levels are preferredbecause they provide, after conversion, the desired cationic chargedensity in the resinous products useful in cathodic electrodeposition.These cationic resins are produced by conversion of part or all of theepoxy groups to cationic groups as described below.

Reaction of the monofunctional compound with epoxy groups of thepolyglycidylether components of the reaction mixture can be done priorto, substantially simultaneously with, or subsequent to thechain-extension reactions of the aromatic hydroxyl-containing productand the polyglycidylether components.

Reactions of the above components to produce the advanced epoxy resinsare typically conducted by mixing the components and heating, usually inthe presence of a suitable catalyst, to temperatures between 125° C. and200° C., preferably between 150° C. and 180° C., until the desiredepoxide content of the product is reached. The reaction can, optionally,be conducted in an appropriate solvent to reduce the viscosity,facilitate mixing and handling, and assist in controlling the heat ofreaction.

Many useful catalysts for the desired reactions are known in the art.Examples of suitable catalysts include ethyltriphenylphosphoniumacetate.acetic acid complex; ethyltriphenylphosphonium chloride,bromide, iodide, or phosphate; and tetrabutylphosphonium acetate.aceticacid complex. The catalysts are typically used at levels of from about0.0001 to about 0.01 mole of catalyst per epoxide group.

Appropriate solvents include aromatic solvents, glycol ethers, glycolether esters, high boiling esters or ketones, or mixtures. Other usefulsolvents will be apparent to those skilled in the art. Preferredsolvents include, for example, xylene, ethylene glycol monobutyletherand propylene glycol monophenylether. Solvent content can range fromzero to 30 percent of the reaction mixture. A solvent is usually chosenwhich is compatible with the subsequent cation-forming reactions andwith the final coating composition so that the solvent does not requiresubsequent removal or one that can be readily removed.

Unexpectedly, the two step preparation of the advanced epoxy resinprovides an improvement in raising the electrodeposition rupture voltageand lowering the conductivity of the aqueous coating compositioncomprising advanced cationic resin(s) produced by the two steppreparation and consequently improving the appearance of the coatings,especially at higher electrodeposition voltages, as compared to a onestep preparation wherein components (1a), (1b), and (2) are reactedtogether simultaneously.

The nucleophilic compounds which are used advantageously in forming thecations required for forming the cationic resins in this invention arerepresented by the following classes of compounds, sometimes calledLewis bases:

(a) monobasic heteroaromatic nitrogen compounds;

(b) tetra (lower alkyl)thioureas;

(c)R¹ --S--R² wherein R¹ and R² individually are lower alkyl, hydroxylower alkyl or are combined as one divalent acyclic aliphatic radicalhaving 3 to 5 carbon atoms; ##STR9## wherein R² and R³ individually arelower alkyl, hydroxy lower alkyl, ##STR10## or are combined as onedivalent acyclic aliphatic radical having from 3 to 5 carbon atoms, R⁴is a divalent acyclic aliphatic group having from 2 to 10 carbon atoms,R⁵ and R⁶ individually are lower alkyl and R¹ is hydrogen or loweralkyl, aralkyl or aryl, except that when R² and R³ together are adivalent acyclic aliphatic group then R¹ is hydrogen, lower alkyl orhydroxyalkyl and when either or both of R² and R³ is ##STR11## then R¹is hydrogen; or ##STR12## wherein R¹, R² and R³ individually are loweralkyl, hydroxy lower alkyl or aryl.

In this specification the term lower alkyl means an alkyl having from 1to 6 carbon atoms such as methyl, ethyl, propyl, isopropyl, n-butyl,isobutyl, n-pentyl, isopentyl, n-hexyl and isohexyl or branch chainisomers thereof.

Representative specific nucleophilic compounds are pyridine,nicotinamide, quinoline, isoquinoline, tetramethyl thiourea, tetraethylthiourea, hydroxyethylmethyl sulfide, hydroxyethylethyl sulfide,dimethyl sulfide, diethyl sulfide, di-n-propyl sulfide, methyl-n-propylsulfide, methylbutyl sulfide, dibutyl sulfide, dihydroxyethyl sulfide,bis-hydroxybutyl sulfide, trimethylene sulfide, thiacyclohexane,tetrahydrothiophene, dimethyl amine, diethyl amine, dibutyl amine,2-(methylamino)ethanol, diethanolamine and the ketimine derivatives ofpolyamines containing secondary and primary amino groups such as thoseproduced by the reaction of diethylene triamine orN-aminoethylpiperazine with acetone, methyl ethyl ketone ormethylisobutyl ketone; N-methylpiperidine, N-ethylpyrrolidine,N-hydroxyethylpyrrolidine, trimethylphosphine, triethylphosphine,tri-n-butylphosphine, trimethylamine, triethylamine, tri-n-propylamine,tri-isobutylamine, hydroxyethyldimethylamine, butyldimethylamine,trihydroxyethylamine, triphenylphosphorus, andN,N,N-dimethylphenethylamine, methyldiethanolamine,dimethylethanolamine, any combination thereof and the like.

The nucleophilic compound is employed in an amount sufficient to convertleast a portion of the epoxy groups to cationic groups or cation-forminggroups. When the nucleophilic compound is added to the epoxy-containingcompound in the presence of an acid, a cationic group is formed. Whenthe nucleophilic compound is added to the epoxy-containing compound inthe absence of an acid, an adduct of the epoxy-containing compound andthe nucleophilic compound is formed which is a cation-forming groupwhich forms a cationic group when an acid is added.

Substantially any organic acid, especially a carboxylic acid, can beused in the conversion reaction to form onium salts so long as the acidis sufficiently strong to promote the reaction between the nucleophiliccompound and the vicinal epoxide group(s) on the resinous reactant. Inthe case of the salts formed by addition of acid to a secondaryamine-epoxy resin reaction product, the acid should be sufficientlystrong to protonate the resultant amine product to the extent desired.

Monobasic acids are normally preferred (H.sup.⊕ A.sup.⊖). Suitableorganic acids include, for example, alkanoic acids having from 1 to 4carbon atoms (e.g., acetic acid, formic acid, propionic acid, etc.),alkenoic acids having up to 5 carbon atoms (e.g., acrylic acid,methacrylic acid, etc.) hydroxy-functional carboxylic acids (e.g.,glycolic acid, lactic acid, etc.) and organic sulfonic acids (e.g.,methanesulfonic acid), and the like. Presently preferred acids are loweralkanoic acids of 1 to 4 carbon atoms with lactic acid and acetic acidbeing most preferred. The anion can be exchanged, of course, byconventional anion exchange techniques. See, for example, U.S. Pat. No.3,959,106 at column 19. Suitable anions are bisulfate, bicarbonate,nitrate, dihydrogen phosphate, lactate and alkanoates of 1-4 carbonatoms. Acetate and lactate are the most preferred anions. Halide anionsare usable, but are not preferred.

The conversion reaction to form cationic resins is normally conducted bymerely blending the reactants together and maintaining the reactionmixture at an elevated temperature until the reaction is complete orsubstantially complete. The progress of the reaction is easilymonitored. The reaction is normally conducted with stirring and isnormally conducted under an atmosphere of inert gas (e.g., nitrogen).Satisfactory reaction rates occur at temperatures of from 25° C. to 100°C., with preferred reaction rates being observed at temperatures from60° to 100° C.

Good results can be achieved by using substantially stoichiometricamounts of reactants although a slight excess or deficiency of theepoxy-containing resin or the nucleophilic compounds can be used. Withweak acids, useful ratios of the reactants range from 0.5 to 1.0equivalent of nucleophilic compounds per epoxide group of the resin and0.4 to 1.1 equivalents of organic acid per epoxide. These ratios, whencombined with the preferred epoxide content resins described above,provide the desired range of cationic charge density required to producea stable dispersion of the coating composition in water. With stillweaker acids (e.g., a carboxylic acid, such as acetic acid) a slightexcess of acid is preferred to maximize the yield of onium salts. Inpreparing the compositions in which the cationic group being formed isan onium group, the acid should be present during the reaction of thenucleophilic compounds and the epoxy group of the resin. When thenucleophilic compounds is a secondary amine, the amine-epoxy reactioncan be conducted first, followed by addition of the organic acid to formthe salt and thus produce the cationic form of the resin. Largerexcesses of amine can be used and the excess amine subsequently removedas known in the art such as by vacuum distillation, steam distillation,falling film distillation, and the like.

For the onium-forming reactions, the amount of water that is alsoincluded in the reaction mixture can be varied to convenience so long asthere is sufficient acid and water present to stabilize the cationicsalt formed during the course of the reaction. Normally, it has beenfound preferable to include water in the reaction in amounts of from 5to 30 moles per epoxy equivalent. When the nucleophilic compound is asecondary amine, the water can be added before, during, or after theresin epoxy group/nucleophile reaction. The preferred range of chargedensity of the cationic, advanced epoxy resin is from 0.2 to 0.8milliequivalent of charge per gram of the resin, calculated assumingcomplete salting of the limited reagent (acid or amine).

It has also been found advantageous to include minor amounts ofwater-compatible organic solvents in the reaction mixture. The presenceof such solvents tends to facilitate contact of the reactants andthereby promote the reaction rate. In this sense, this particularreaction is not unlike many other chemical reactions and the use of suchsolvent modifiers is conventional. The skilled artisan will, therefore,be aware of which organic solvents can be included.

When a desired degree of reaction is reached, any excess nucleophiliccompound can be removed by standard methods, e.g., dialysis, vacuumstripping and steam distillation.

The cationic, advanced epoxy resins of this invention in the form ofaqueous dispersions are useful as coating compositions, especially whenapplied by electrodeposition. The coating compositions containing thecationic resins of this invention as the sole resinous component areuseful but it is preferred to include crosslinking agents in the coatingcomposition so that the coated films, when cured at elevatedtemperatures, will be crosslinked and exhibit improved film properties.The most useful sites on the resin for crosslinking reactions are thesecondary hydroxyl groups along the resin backbone. Materials suitablefor use as crosslinking agents are those known to react with hydroxylgroups and include blocked polyisocyanates; amine-aldehyde resins suchas melamine-formaldehyde, urea-formaldehyde, benzoguanine-formaldehyde,and their alkylated analogs; polyester resins; and phenol-aldehyderesins.

Particularly useful and preferred crosslinking agents are the blockedpolyisocyanates which, at elevated temperatures, react with the hydroxylgroups of the resin to crosslink the coating. Such crosslinkers aretypically prepared by reaction of the polyisocyanate with amonofunctional active-hydrogen compound.

Examples of polyisocyanates suitable for preparation of the crosslinkingagent are described in U.S. Pat. No. 3,959,106 to Bosso, et al., inColumn 15, lines 1-24 which is incorporated herein by reference. Alsosuitable are isocyanate-functional prepolymers derived frompolyisocyanates and polyols using excess isocyanate groups. Examples ofsuitable prepolymers are described by Bosso, et al., in U.S. Pat. No.3,959,106, Column 15, lines 25-57. Additional suitable blockedpolyisocyanates are described in U.S. Pat. No. 4,711,917 to McCollum etal. and European Patent Application 0,236,050 which are incorporatedherein by reference in their entirety. In the preparation of theprepolymers, reactant functionality, equivalent ratios, and methods ofcontacting the reactants must be chosen in accordance withconsiderations known in the art to provide ungelled products having thedesired functionality and equivalent weight.

Preferred polyisocyanates are the isocyanurate trimer of hexamethylenediisocyanate, toluene diisocyanate, methylene diphenylene diisocyanate(MDI), polymeric MDI, isophorone diisocyanate and prepolymers of toluenediisocyanate or methylene diphenylene diisocyanate or the like withtrimethylolpropane, dipropylene glycol, tripropylene glycol, otherpolyols or mixtures thereof.

Suitable blocking agents include alcohols, phenols, oximes, lactams, andN,N-dialkylamides or esters of alpha-hydroxyl group containingcarboxylic acids. Examples of suitable blocking agents are described inU.S. Pat. No. 3,959,106 to Bosso, et al., in Column 15, line 58, throughColumn 16, line 6, and in U.S. Pat. No. 4,452,930 to Moriarity.

The blocked polyisocyanates are prepared by reacting equivalent amountsof the isocyanate and the blocking agent in an inert atmosphere such asnitrogen at temperatures between 25° to 100° C., preferably below 70° C.to control the exothermic reaction. Sufficient blocking agent is used sothat the product contains no residual, free isocyanate groups. A solventcompatible with the reactants, product, and the coating composition canbe used such as a ketone or an ester. A catalyst can also be employedsuch as dibutyl tin dilaurate.

The blocked polyisocyanate crosslinking agents are incorporated into thecoating composition at levels corresponding to from 0.2 to 2.0 blockedisocyanate groups per hydroxyl group of the cationic resin. Thepreferred level is from about 0.3 to about 1 blocked isocyanate groupper resin hydroxyl group.

A catalyst can, optionally, be included in the coating composition toprovide faster or more complete curing of the coating. Suitablecatalysts for the various classes of crosslinking agents are known tothose skilled in the art. For the coating compositions using the blockedpolyisocyanates as crosslinking agents, suitable catalysts includedibutyl tin dilaurate, dibutyl tin diacetate, dibutyl tin oxide,stannous octanoate, and other urethane-forming catalysts known in theart. Amounts used typically range between 0.1 and 3 weight percent ofbinder solids.

Unpigmented coating compositions are prepared by blending the cationicresinous product with the crosslinking agent and optionally anyadditives such as catalysts, solvents, surfactants, flow modifiers,plasticizers, defoamers, or other additives. This mixture is thendispersed in water by any of the known methods. A preferred method isthe technique known as phase-inversion emulsification, wherein water isslowly added with agitation to the above mixture, usually attemperatures ranging from ambient to 70° C., until the phases invert toform an organic phase-in-water dispersion. The solids content of theaqueous dispersion is usually between 5 and 30 percent by weight andpreferably between 10 and 25 percent by weight for application byelectrodeposition.

Pigmented coating compositions are prepared by adding a concentrateddispersion of pigments and extenders to the unpigmented coatingcompositions. This pigment dispersion is prepared by grinding thepigments together with a suitable pigment grinding vehicle in a suitablemill as known in the art.

Pigments and extenders known in the art are suitable for use in thesecoatings including pigments which increase the corrosion resistance ofthe coatings. Examples of useful pigments or extenders include titaniumdioxide, talc, clay, lead oxide, lead silicates, lead chromates, carbonblack, strontium chromate, and barium sulfate.

Pigment grinding vehicles are known in the art. A pigment grindingvehicle suitable for use with this invention consists of a water-solublecationic resinous product, water, and a minor amount of water-compatiblesolvent. The cationic resinous product is prepared by reacting anepichlorohydrin/bisphenol A condensation product having an epoxide groupcontent of 8 percent with a nucleophilic compound, an acid, and water ina similar fashion as described above for the cationic resins used in thepreferred embodiment of the invention. The water-soluble product can bediluted with water to form a clear solution useful as a pigment grindingvehicle.

The pH and/or conductivity of the coating compositions can be adjustedto desired levels by the addition of compatible acids, bases, and/orelectrolytes known in the art. Other additives such as solvents,surfactants, defoamers, anti-oxidants, bactericides, etc. can also beadded to modify or optimize properties of the compositions or thecoating in accordance with practices known to those skilled in the art.

Although the coating compositions of the invention can be applied by anyconventional technique for aqueous coatings, they are particularlyuseful for application by cathodic electrodeposition, wherein thearticle to be coated is immersed in the coating composition and made thecathode, with a suitable anode in contact with the coating composition.When sufficient voltage is applied, a film of the coating deposits onthe cathode and adheres. Voltage can range from 10 to 1,000 volts,typically 50 to 500. The film thickness achieved generally increaseswith increasing voltage. In the case of the coating compositions of theinvention, suitable films may be achieved at higher voltages than forcompositions using resins prepared by a one-step preparation. Current isallowed to flow for between a few seconds to several minutes, typicallytwo minutes over which time the current usually decreases. Anyelectrically conductive substrate can be coated in this fashion,especially metals such as steel and aluminum. Other aspects of theelectrodeposition process, such as bath maintenance, are conventional.After deposition, the article is removed from the bath and typicallyrinsed with water to remove that coating composition which does notadhere.

The uncured coating film on the article is cured by heating at elevatedtemperatures, ranging from 200° F. to 400° F. (93° C. to 204° C.), forperiods of 1 to 60 minutes.

All of the coating compositions of the invention provide usefulcathodically electrodepositable coatings having improved flowout, filmbuild, and deposition properties and appearance due to use of thetwo-step preparation of the advanced epoxy resin composition.

The noncationic advanced resins of the present invention are useful inconventional solvent-borne coating compositions comprising epoxy resinsof similar epoxide equivalent weight.

They can be formulated with any suitable curing agent for curingadvanced epoxy resins either by reaction of the terminal epoxide groupsor by the aliphatic hydroxyl groups pending from the chain which resultfrom the reaction of the glycidyl ether groups with the phenolichydroxyl groups during preparation of the advanced resin.

Any of the known curing agents for curing epoxy resins are suitable andinclude, polyamines, polyamides, polyisocyanates, blockedpolyisocyanates, amino resins, phenolic resins, and polyesters and thelike. Particularly suitable such curing agents for cathodicelectrodeposition applications include, blocked polyisocyanates such as,for example, methylene diphenylene diisocyanate or isocyanate terminatedprepolymers thereof which have been blocked with lower alkanols 1 toabout 8 carbon atoms or glycol ethers having from about 3 to about 9carbon atoms, isocyanate terminated toluene diisocyanate prepolymersblocked similarly to that described above, polymethylene polyphenyleneisocyanate blocked similarly to that described above.

The following examples are illustrative of the invention, but are not tobe construed as to limiting the scope thereof in any manner.

Blocked Isocyanate Crosslinker Solution A

An isocyanate terminated prepolymer of methylenediphenyl diisocyanateand a polypropylene glycol having a hydroxyl equivalent weight of about80 and said prepolymer having an NCO equivalent weight of 181 in anamount of 1,955.6 g (10.8 eq) and xylene in an amount of 484.3 g arecharged to a reactor and heated to 50° C. Acetone oxime in an amount of788.7 g (10.8 eq) is then added as a solid in portions over a 75 minuteperiod while maintaining the reaction temperature near 50° C. withcooling. During the final 30 minutes of the feed, the temperature isallowed to rise to 60° C. to decrease the viscosity of the mixture.After the feed is completed, 0.7 g of dibutyltin dilaurate is added andthe reaction temperature raised to 70° C. over a 30 minute period. Themixture is reacted at 70° C. for 105 minutes, recovered, and poured intoglass bottles for storage.

Blocked Isocyanate Crosslinker Solution B

Toluene diisocyanate (1363.1 g, 15.67 NCO equiv.) is charged to a 5liter, round-bottomed flask equipped with a condenser, mechanicalstirrer, nitrogen inlet, addition funnel and thermometer. The materialis heated to 58° C. and a mixture of 308.9 g (1.45 OH equiv.) ofpolypropylene glycol of average molecular weight of 425 and 1.29 g ofT-12 (dibutyltin dilaurate) catalyst is added dropwise with cooling tomaintain 58° C. An additional 523.5 g (2.46 OH equiv.) of thepolypropylene glycol is added afterward. The total time for the twofeeds is 140 minutes. 2-Ethylhexanol (1527.6 g, 11.75 OH equiv.) is thenadded over a period of 220 minutes at 58° C.-63° C. The reaction mixtureis then heated at 73° C. for 45 minutes and the resulting blockedisocyanate crosslinker is a clear, viscous liquid at room temperature.

Pigment Grinding Vehicle A

Into a 5 liter, round-bottomed flask equipped with condenser, additionfunnel, nitrogen inlet, mechanical stirrer, and thermometer is charged920.5 g (4.90 eq) of a diglycidyl ether of bisphenol A having an EEW of188 and 298.1 g (2.61 eq) bisphenol A. The mixture is heated undernitrogen to 85° C. and 1.44 g (2.46 eq) of a 70% solution of ethyltriphenylphosphonium acetate.acetic acid complex in methanol is added.The mixture is heated to 150° C. and allowed to exotherm to 184° C. Thetemperature is brought down to 175° C. and the reaction is maintained at175° C. for one hour. The resin is cooled to 83° C. and diluted with304.6 g methyl ethyl ketone. The solution is cooled to 65° C. and 167.5g (2.23 eq) of N-methyl,2-aminoethanol is added over 19 minutes at 64°C.-70° C. The reaction is heated to 80° C.-84° C. for 65 minutes. Thesolution is then cooled to 75° C. and 276.8 g of 72.5% lactic acidsolution (2.23 eq) in water is added. The mixture is then diluted withwater to an approximately 40% non-volatile content to produce a clear,viscous solution.

Blocked Isocyanate Crosslinker Solution C

Methylenediphenylene diisocyanate (MDI) having 48% by weight content of2,4' isomer and an isocyanate equivalent weight of 125.2 g/eq (10,746 g,85.83 eq), methylisobutylketone (8,849 g) and dibutyltin dilaurate (15g) are charged to a reactor and heated to 60° C. A mixture ofdipropylene glycol (250 g, 3.73 eq), tripropylene glycol (350 g, 3.65eq) and 2-butoxyethanol (9,340 g, 79.15 eq) is then added at a rate tokeep the reaction below 70° C. After the addition is completed, thetemperature is raised to 90° C. for 30 minutes. An infrared spectralanalysis of the product showed no isocyanate present. After 30 minutesadditional reaction time at 90° C., the product was transferred tocontainers and cooled.

Pigment Dispersion A

Into a one gallon, metal paint can is placed 698.0 g of pigment vehicleA, 108.3 g ASP 200 clay, 41.9 g EP202 lead silicate, 14.7 g Raven 410carbon black, and 537.0 g R-900 titanium dioxide. A volume of aboutone-half the bulk pigment volume of chrome-plated steel diagonals isadded and the pigments are ground and dispersed by shaking the sealedpaint can on a paint shaker. Water is added as the grinding progresseduntil a total of 186.0 g of water had been added. The diagonals areremoved by passing the dispersion through a screen. The pigmentdispersion contained 44.2% pigments by weight.

Pigment Dispersion B

Pigment Dispersion B is a commercially available pigment paste forcathodic electrodeposition available from PPG Industries, Inc.,Automotive Electrocoat Office, Cleveland, Ohio under the designationE5994, ED-4 pigment paste. The product is 64% solids by weight,comprised of 11% resin vehicle and 53% pigment solids.

Surfactant Mixture A

A surfactant mixture known in the art is formed by mixing 80 gCiba-Geigy Amine C, 80 g Air Products Surfynol 104, 105 g2-butoxyethanol, 14.7 g acetic acid and 225 g water with heating todissolve. The solution is filtered and then cooled to form a turbid,hazy solution.

EXAMPLE 1 A. Preparation of Advanced Epoxy Resin by Two Step Procedure

A diglycidyl ether of dipropylene glycol having an epoxide equivalentweight (EEW) of 182.6 in an amount of 235.5 g (1.29 eq) and bisphenol Ain an amount of 333.3 g (2.92 eq) are charged to a reactor, stirredunder nitrogen and heated to 80° C. A 70% solution oftetrabutylphosphonium acetate.acetic acid complex in methanol in anamount of 2.3 g (5.07 meq) is added and the mixture heated to 175° C.The reaction is allowed to exotherm to 180° C. and then maintained at175° C. for 30 minutes. The product is cooled to 150° C. and adiglycidyl ether of bisphenol A having an EEW of 187.6 in an amount of549.6 g (2.93 eq) is added. The mixture cooled to 130° C. and isreheated to 175° C. for 58 minutes, then cooled. The epoxide equivalentweight at this point is found to be 943 g/eq.

B. Preparation of Cationic Resin

Xylene in an amount of 58.7 g is added to the product from A above andthe solution cooled to 80° C. Diethanolamine in an amount of 124.4 g(1.18 eq) is added and the mixture reacted at 100° C. one hour. Theproduct shows 0.913 meq base/g solids at 95.5% solids. This amine adductsolution in an amount of 237.0 g is blended with 142.9 g of blockedisocyanate crosslinker solution A at 59° C. and 4.9 g dibutyltindilaurate catalyst is added. A solution of 22.8 g of 73.5% lactic acidin 46 g water is added dropwise at 64° C.-72° C., followed by dropwiseaddition of water at 56° C.-65° C. until inversion. The dispersion iscooled and diluted to 18% non-volatiles. A total of 1644.7 g water isused.

COMPARATIVE EXPERIMENT A A. One step procedure for the preparation of anadvanced epoxy resin

A diglycidyl ether of dipropylene glycol having an EEW of 182.2 in anamount of 539.2 g (2.96 eq), a diglycidyl ether of bisphenol A having anEEW of 187.5 in an amount of 1258.2 g (6.71 eq), and bisphenol A in anamount of 763.7 g (6.69 eq) are charged to a reactor and heated to 80°C. under nitrogen. A 70% solution of ethyltriphenylphosphoniumacetate.acetic acid complex in methanol in an amount of 6.51 g (11.1meq) is added and the mixture is heated to 150° C. The reaction isallowed to exotherm to 192° C., then controlled at 175° C. for 25minutes. The reaction is then cooled to 150° C. for 45 minutes. Theepoxide equivalent weight is 869 g/eq at this point.

B. Preparation of Cationic Resin

The product from A above is cooled to 135° C. and 133.3 g xylene isadded. The solution is further cooled to 85° C., and diethanolamine(306.7 g, 2.92 eq) is added. The temperature rose to 105° C. and thenthe reaction is cooled to 95° C. for one hour. The product shows 0.978meq base/g solids at 95.5% solids, as titrated with 0.1N HCl in methanolusing tetrahydrofuran (THF) as solvent.

This amine adduct resin solution (235.8 g) is heated to 76° C. and 142.9g of the blocked isocyanate crosslinker solution A at 75° C. is added.The two are mixed at 70° C. and 4.9 g dibutyltin dilaurate catalyst isadded. A solution of 24.3 g of 73.5% lactic acid in 48.7 g water is thenadded dropwise over 12 minutes at 73° C.-76° C. Water is then addeddropwise between 73° C. and 62° C. until inversion to form an aqueousdispersion of the resin is noted. The dispersion is then cooled anddiluted to 18% non-volatile content with water. A total of 1644.3 gwater is used.

EXAMPLE 2 A. Preparation of Advanced Epoxy Resin by two step procedure

A diglycidyl ether of dipropylene glycol having an EEW of 181.7 in anamount of 214.4 g (1.18 eq) and bisphenol A in an amount of 328.0 g(2.88 eq) are charged to a reactor and heated under nitrogen to 80° C. A70% solution of ethyltriphenylphosphonium acetate.acetic acid complex inmethanol (1.66 g, 2.83 meq) is added and the mixture is heated to 175°C. and held there for 30 minutes. The product is cooled to 150° C. and adiglycidyl ether of bisphenol A having an EEW of 187.4 in an amount of500.3 g (2.67 eq) is added. The mixture cooled to 88° C. and anadditional 0.82 g (1.4 meq) of the ethyltriphenylphosphoniumacetate.acetic acid solution is added. The reaction mixture is reheatedto 175° C. and maintained there for 29 minutes. The epoxide equivalentweight at this point is 1144 g/eq.

B. Preparation of Cationic Resin

The product from A above is cooled and diluted with 53.9 g of xylene.The solution is further cooled to 92° C. Diethanolamine (94.1 g, 0.895eq) is then added and the reaction exothermed to 110° C. The reactionmixture is maintained between 100° and 110° C. for one hour. The productshows 0.768 meq base/g solids at 95.4% solids.

This amine adduct solution in an amount of 222.2 g is blended with 132.5g of blocked isocyanate crosslinker A at about 70° C. and 4.4 gdibutyltin dilaurate catalyst is added. A solution of 18.0 g of 73.5%lactic acid in 36.2 g water is added dropwise with mixing. Water is thenadded dropwise between 61° C. and 67° C. until inversion. The dispersionis then cooled and diluted to 18% non-volatiles. A total of 1524.0 gwater is used.

COMPARATIVE EXPERIMENT B A. One step procedure for the preparation of anadvanced epoxy resin

A diglycidyl ether of bisphenol A having an EEW of 187.4 in an amount of500.3 g (2.67 eq), a diglycidyl ether of dipropylene glycol having anEEW of 181.7 in an amount of 214.4 g (1.18 eq), and bisphenol A in anamount of 328.0 g (2.88 eq) are charged to a reactor and heated undernitrogen to 80° C. A 70% solution of ethyltriphenylphosphoniumacetate.acetic acid complex in methanol in an amount of 2.48 g (4.23meq) is added and the mixture heated to 150° C. The reaction exothermedto 174° C. and is then maintained at 175° C. for 31 minutes. The epoxideequivalent weight is 1123 g/eq at this point.

B. Preparation of Cationic Resin

The resin from A above is cooled and 53.7 g xylene added. The solutionis further cooled to 86° C. and 95.5 g (0.91 eq) of diethanolamine isadded. The reaction mixture exothermed to 108° C. and is then controlledat 100° C. for one hour. The product shows 0.775 meq base/g solids at95.5% solids.

This amine adduct solution in an amount of 221.5 g is blended with 132.2g of blocked isocyanate crosslinker solution A at 67° C. and 4.6 g ofdibutyltin dilaurate catalyst is added. A solution of 18.1 g of 73.5%lactic acid in 37.1 g water is added dropwise with mixing at 69° C.-73°C. Water is then added dropwise between 62° C. and 69° C. untilinversion. The aqueous dispersion is cooled and diluted to 18%non-volatiles. A total of 1522.5 g of water is used.

EXAMPLE 3

The aqueous resin dispersions from Examples 1 and 2 and the ComparativeExperiments A and B are pigmented by adding, with continuous stirring,an appropriate amount of Pigment Dispersion A to yield a pigment tobinder weight ratio of 0.2, with binder counted as the solids in theresin dispersion and pigment vehicle. The pigmented dispersion served asthe coating bath for electrodeposition.

Pretreated (Bonderite 40), unpolished cold rolled steel test panels aresuspended in the bath and are electrocoated by application of thedesired D.C. voltage between the panel and the steel container (servingas the anode). Coating is done at 80° F. with the bath continuallystirred. The voltage is typically applied in ramp fashion from zerovolts up to coating voltage over 15-30 seconds. Voltage is applied for atotal of two minutes. After coating, excess bath is rinsed from thepanels by a gentle stream of deionized water. The panels are cured bybaking in an electric forced convection oven at 135° C. for 15 minutes.

Results of electrodeposition coating of the coating baths made from theexamples and the Comparative Experiments are summarized in Table I.

The results in Table I show the higher rupture voltages obtained usingresins made by the two-step advancement process of the present inventionas compared to the one step process. The resins prepared by the two-stepprocess also gave better appearance in each case.

EXAMPLE 4

Into a 2 liter, round bottomed flask fitted with nitrogen inlet,mechanical stirrer, condenser, and thermometer is charged 88.9 g (0.494equiv.) of a diglycidyl ether of bisphenol A epoxy resin having anepoxide equivalent weight of 180, 66.3 g (0.202 equiv.) of a productwhich is substantially the diglycidyl ether

                  TABLE I                                                         ______________________________________                                                 Coating Designation                                                           A         B          C*                                              ______________________________________                                        Cationic Resin                                                                           Ex. 1       Ex. 2      C.E.B                                       employed                                                                      EEW of     943         1144       1123                                        Advanced Resin                                                                from which the                                                                Cationic Resin                                                                was made                                                                      Rupture    225          275        150                                        Voltage.sup.a                                                                 Coating thickness                                                             mils (volts)                                                                             0.2 (75)    0.29 (150)  0.63 (125)                                 mm (volts) 0.0051 (75) 0.0074 (150)                                                                             0.016 (125)                                 Coating thickness                                                             mils (volts)                                                                             0.39 (200)   0.5 (250) --                                          mm (volts) 0.01 (200)  0.013 (250)                                                                              --                                          Coating    Fair        Good       Poor                                        Appearance                                                                    ______________________________________                                         *Not an example of the present invention.                                     .sup.a Rupture voltage is the voltage at which electrodeposition becomes      uncontrolled and excessive gassing and deposition take place, due to lack     of current cutoff as the deposit builds.                                 

of an adduct of four moles of ethylene oxide and one mole of bisphenol A(epoxide equivalent weight of 328, prepared by treating the adduct ofbisphenol A and ethylene oxide with epichlorohydrin in the presence ofLewis acid catalyst, followed by treatment with sodium hydroxide), and336.6 g (2.95 equiv.) bisphenol A. The mixture is heated to 70° C. and1.41 g of a 47 percent solution of ethyltriphenyl phosphonium phosphatein methanol is added. The mixture is heated to 180° C. for three hours.The resin is cooled to 120° C. and 509 g (2.83 equiv.) of a diglycidylether of bisphenol A having an EEW of 180 is added. The mixture isheated to 180° C. and held at that temperature for two hours. Theepoxide equivalent weight of the resultant product is 1954. The resin iscooled and diluted with propylene glycol methyl ether to 80 percentnon-volatile content by weight.

This resin solution (263.6 g resin solution, 210.88 g of neat resin,0.108 equiv.) is heated under nitrogen to 85° C. and 8.07 g (0.108equiv.) of 2-(methylamino)ethanol is added. The reaction mixture ismaintained at 82° to 85° C. for one hour. Blocked isocyanate CrosslinkerSolution B (94.7 g), T-12 (dibutyltin dilaurate) catalyst (4.8 g), and72.9 percent lactic acid solution (10.7 g, 0.087 equiv.) mixed with 11.7g water are added sequentially and mixed. Water is added dropwise over aperiod of 3 hours at temperatures between 82° and 60° C. until themixture inverted to form an aqueous dispersion. The dispersion is thencooled and further diluted with water to a non-volatile content of 18percent.

The aqueous dispersion (1,803.9 g) is pigmented with 172.0 g of pigmentdispersion A. The coating composition is placed in a stainless steeltank, agitated, and maintained at 80° F. (27° C.). Unpolished steel testpanels having Bonderite™ 40 treatment and P60 rinse (available fromAdvanced Coating Technologies, Inc.) are immersed in the tank andconnected as the cathode to a D.C. voltage source, with the tank wallsserving as the anode. The desired voltage is applied for two minutes,then the panels are removed, rinsed with deionized water, and baked atthe 177° C. for 30 minutes. The resulting film thicknesses at theindicated voltage are given in Table II

                  TABLE II                                                        ______________________________________                                        Deposition Voltage                                                                           Film Thickness, mil (mm)                                       ______________________________________                                        200            0.16 (0.00410)                                                 225            0.19 (0.00480)                                                 250            0.21 (0.00530)                                                 275            0.23 (0.0058)                                                  300            0.27 (0.0069)                                                  350            0.34 (0.0086)                                                  ______________________________________                                    

EXAMPLE 5 A. Preparation of Advanced Epoxy Resin by Two Step Procedure

A diglycidyl ether of an adduct of one mole bisphenol A and about 3.4moles (per mole bisphenol A on the average) propylene oxide having anepoxide equivalent weight (EEW) of 341 g/eq and containing 2.99 wt %total chlorides (272.2 g, 0.798 eq), bisphenol A (232.7 g, 2.04 eq) and45.0 g xylene are charged to a reactor and heated under nitrogen to 88°C. A 70% solution of ethyltriphenylphosphonium acetate.acetic acidcomplex in methanol (1.19 g, 2.03 meq) is added and the mixture isheated to 175° C. and held there for 30 minutes. The product is cooledto below 150° C. and a diglycidyl ether of bisphenol A having an EEW of188 g/eq (395.1 g, 2.10 eq) is added. The mixture cooled to 108° C. Thereaction mixture is reheated to 175° C. and maintained there for 68minutes. The epoxide equivalent weight (EEW) at this point is 1059 g/eq,based on non-volatiles.

B. Preparation of Cationic Resin

The above product is cooled to below 115° C. and 276.9 gmethylisobutylketone is added. The solution is further cooled to 96° C.Diethanolamine at 1 eq/eq epoxide in the reactor (87.5 g, 0.833 eq) isthen added and the reaction exothermed to 108° C. The reaction mixtureis then maintained at 100° C. for two hours. The product showed 0.816meq base/g solids at 79.4% solids.

A portion of this amine adduct solution (250 g of solids) is blendedwith 142.9 g of blocked isocyanate crosslinker solution C at ambienttemperature. Propylene glycol phenyl ether (10.5 g), Surfactant MixtureA (5.6 g) and acetic acid (0.8 eq/eq base in the amine adduct) are thenadded and mixed. Water is then added dropwise until inversion. Thedispersion is then diluted to 30-35% non-volatiles with water. Themethylisobutylketone and xylene are evaporated out of the aqueousdispersion by stirring two days under a gentle stream of nitrogen.

EXAMPLE 6 A. Preparation of Advanced Epoxy Resin by Two Step Procedure

A diglycidyl ether of an adduct of one mole bisphenol A and about 6moles (per mole bisphenol A on the average) ethylene oxide having anepoxide equivalent weight of 366 g/eq (292.1 g, 0.798 eq), bisphenol A(225.2 g, 1.98 eq) and 45.0 g xylene are charged to a reactor and heatedunder nitrogen to 90° C. A 70% solution of ethyltriphenylphosphoniumacetate.acetic acid complex in methanol (1.16 g, 1.98 meq) is added andthe mixture is heated to 175° C. and held there for 30 minutes. Theproduct is cooled to below 150° C. and a diglycidyl ether of bisphenol Ahaving an EEW of 188 g/eq (382.7 g, 2.04 eq) is added. The mixturecooled to 107° C. The reaction mixture is reheated to 175° C. andmaintained there for 81 minutes. The epoxide equivalent weight (EEW) atthis point is 1086 g/eq, based on non-volatiles.

B. Preparation of Cationic Resin

The above product is cooled to below 115° C. and 283.8 gmethylisobutylketone (MIBK) is added. The solution is further cooled to93° C. Diethanolamine at 1 eq/eq epoxide in the reactor (85.1 g, 0.810eq) is then added and the reaction exothermed to 103° C. The reactionmixture is then maintained at 100° C. for two hours. The product showed0.784 meq base/g solids at 77.9% solids.

A portion of this amine adduct solution (250 g of solids) is blendedwith 142.9 g of blocked isocyanate crosslinker solution C at ambienttemperature. Propylene glycol phenyl ether (10.5 g), surfactant mixtureA (5.6 g) and acetic acid (0.85 eq/eq base in the amine adduct) are thenadded and mixed. Water is then added dropwise until inversion. Thedispersion is then diluted to 30-35% non-volatiles with water. Themethylisobutylketone and xylene are evaporated out of the aqueousdispersion by stirring two days under a gentle stream of nitrogen. Afterevaporation, the dispersion at 35% non-volatiles is viscous. MIBK (114g), acetic acid (1.18 g, corresponding to an additional 0.1 eq/eq basein the amine adduct resin) and water (800 g) are added and thedispersion stirred vigorously for two hours. The solvent is againremoved by evaporation. The resulting dispersion is low in viscosity andstable.

EXAMPLE 7 A. Preparation of Advanced Epoxy Resin by Two Step

A diglycidyl ether of an adduct of one mole bisphenol A and about 3.4moles (per mole bisphenol A on the average) propylene oxide having anepoxide equivalent weight of 392 g/eq and containing about 145 ppm byweight total chlorine (calculated as chloride) (225.9 g, 0.576 eq),bisphenol A (157.0 g, 1.38 eq) and 32.5 g xylene are charged to areactor and heated under nitrogen to 92° C. A 70% solution ofethyltriphenylphosphonium acetate.acetic acid complex in methanol (0.82g, 1.4 meq) is added and the mixture is heated to 175° C. and held therefor 30 minutes. The product is cooled to below 150° C. and a diglycidylether of bisphenol A having an EEW of 188 g/eq (274.1 g, 1.46 eq) isadded. The mixture cooled to 110° C. The reaction mixture is reheated to175° C. and maintained there for 111 minutes. The reaction mixture iscooled to 123° C. and 0.2 g (0.34 meq) of the phosphonium solution aboveis added. The mixture is reheated to 175° C. and reacted 62 minutes. Theepoxide equivalent weight (EEW) at this point is 1029 g/eq, based onnon-volatiles.

B. Preparation of Cationic Resin

The above product is cooled to below 115° C. and 209.0 gmethylisobutylketone is added. The solution is further cooled to ambienttemperature. Later, the solution is reheated to 90° C. Diethanolamine at1 eq/eq epoxide in the reactor (65.1 g, 0.62 eq) is then added and thereaction exothermed to 97° C. The reaction mixture is then maintained at100° C. for two hours. The product showed 0.859 meq base/g solids at76.9% solids.

A portion of this amine adduct solution (250 g of solids) is blendedwith 142.9 g of blocked isocyanate crosslinker solution C at ambienttemperature. Propylene glycol phenyl ether (10.5 g), surfactant mixtureA (5.6 g) and acetic acid (0.8 eq/eq base in the amine adduct) are thenadded and mixed. Water is then added dropwise until inversion. Thedispersion is then diluted to 30-35% non-volatiles with water. Themethylisobutylketone and xylene are evaporated out of the aqueousdispersion by stirring two days under a gentle stream of nitrogen.

EXAMPLE 8 A. Preparation of Advanced Epoxy Resin by Two Step Procedure

A diglycidyl ether of an adduct of one mole bisphenol A and about 3.4moles (per mole bisphenol A on the average) propylene oxide having anepoxide equivalent weight of 341 g/eq and containing 2.99 wt % totalchlorides (272.2 g, 0.798 eq), bisphenol A (136.4 g, 120 eq) and 45.0 gxylene are charged to a reactor and heated under nitrogen to 92° C. A70% solution of ethyltriphenylphosphonium acetate.acetic acid complex inmethanol (1.19 g, 2.03 meq) is added and the mixture is heated to 175°C. and held there for 52 minutes. The product is cooled to below 150° C.and a diglycidyl ether of bisphenol A having an EEW of 188 g/eq (401.5g, 2.14 eq) and bisphenol A (96.3 g, 0.845 eq) is added. The mixturecooled to 94° C. The reaction mixture is reheated to 175° C. andmaintained there for 60 minutes. The epoxide equivalent weight (EEW) atthis point is 1029 g/eq, based on non-volatiles.

B. Preparation of Cationic Resin

The above product is cooled to below 115° C. and 281.1 gmethylisobutylketone is added. The solution is further cooled to 92° C.Diethanolamine at 1 eq/eq epoxide in the reactor (89.6 g, 0.853 eq) isthen added and the reaction exothermed to 100° C. The reaction mixtureis then maintained at 100° C. for two hours. The product showed 0.820meq base/g solids at 79.3% solids.

A portion of this amine adduct solution (250 g of solids) is blendedwith 142.9 g of blocked isocyanate crosslinker solution C at ambienttemperature. Propylene glycol phenyl ether (10.5 g), surfactant mixtureA (5.6 g) and acetic acid (0.85 eq/eq base in the amine adduct) are thenadded and mixed. Water is then added dropwise until inversion. Thedispersion is then diluted to 30-35% non-volatiles with water. Themethylisobutylketone and xylene are evaporated out of the aqueousdispersion by stirring two days under a gentle stream of nitrogen.

EXAMPLE 9 A. Preparation of Advanced Epoxy Resin by Two Step Procedure

A diglycidyl ether of an adduct of one mole bisphenol A and about 3.4moles (per mole bisphenol A on the average) propylene oxide having anepoxide equivalent weight of 341 g/eq and containing 2.99 wt % totalchlorides (272.2 g, 0.798 eq), bisphenol A (111.2 g, 0.975 eq) and 45.0g xylene are charged to a reactor and heated under nitrogen to 96° C. A70% solution of ethyltriphenylphosphonium acetate.acetic acid complex inmethanol (1.19 g, 2.03 meq) is added and the mixture is heated to 175°C. and held there for 62 minutes. The product is cooled to below 150° C.and a diglyeidyl ether of bisphenol A having an EEW of 188 g/eq (397.6g, 2.11 eq) and bisphenol A (121.5 g, 1.07 eq) is added. The mixturecooled to 85° C. The reaction mixture is reheated to 175° C. andmaintained there for 128 minutes. The epoxide equivalent weight (EEW) atthis point is 1019 g/eq, based on non-volatiles.

B. Preparation of Cationic Resin

The above product is cooled to below 115° C. and 282.0 gmethylisobutylketone is added. The solution is further cooled to 92° C.Diethanolamine at 1 eq/eq epoxide in the reactor (90.0 g, 0.857 eq) isthen added and the reaction exothermed to 100° C. The reaction mixtureis then maintained at 95° C. for one hour and then 100° C. for one hour.The product showed 0.822 meq base/g solids at 78.7% solids.

A portion of this amine adduct solution (250 g of solids) is blendedwith 142.9 g of blocked isocyanate crosslinker solution C at ambienttemperature. Propylene glycol phenyl ether (10.5 g), surfactant mixtureA (5.6 g) and acetic acid (0.85 eq/eq base in the amine adduct) are thenadded and mixed. Water is then added dropwise until inversion. Thedispersion is then diluted to 30-35% non-volatiles with water. Themethylisobutylketone and xylene are evaporated out of the aqueousdispersion by stirring two days under a gentle stream of nitrogen.

EXAMPLE 10 A. Preparation of Advanced Epoxy Resin by Two Step Procedure

A diglycidyl ether of an adduct of one mole bisphenol A and about 3.4moles (per mole bisphenol A on the average) propylene oxide having anepoxide equivalent weight of 341 g/eq and containing 2.99 wt % totalchlorides (272.2 g, 0.798 eq) and bisphenol A (232.7 g, 2.04 eq) arecharged to a reactor and heated under nitrogen to 100° C. A 70% solutionof ethyltriphenylphosphonium acetate.acetic acid complex in methanol(1.18 g, 2.01 meq) is added and the mixture is heated to 175° C. andheld there for 42 minutes. The product is cooled to below 150° C. and adiglycidyl ether of bisphenol A having an EEW of 188 g/eq (402.6 g, 2.14eq) and bisphenol A (4.5 g, 0.0395 eq) are added. The mixture cooled to111° C. The reaction mixture is reheated to 175° C. and maintained therefor 95 minutes. The epoxide equivalent weight (EEW) at this point is1051 g/eq.

B. Preparation of Cationic Resin

The above product is cooled to below 115° C. and 280.0 gmethylisobutylketone and 44.2 g xylene are added. The solution isfurther cooled to 93° C. Diethanolamine at 1 eq/eq epoxide in thereactor (88.3 g, 0.841 eq) is then added and the reaction exothermed to102° C. The reaction mixture is then maintained at 100° C. for twohours. The product showed 0.856 meq base/g solids at 76.5% solids.

A portion of this amine adduct solution (250 g of solids) is blendedwith 142.9 g of blocked isocyanate crosslinker solution C at ambienttemperature. Propylene glycol phenyl ether (10.5 g), surfactant mixtureA (5.6 g) and acetic acid (0.85 eq/eq base in the amine adduct) are thenadded and mixed. Water is then added dropwise until inversion. Thedispersion is then diluted to 30-35% non-volatiles with water. Themethylisobutylketone and xylene are evaporated out of the aqueousdispersion by stirring two days under a gentle stream of nitrogen.

COMPARATIVE EXPERIMENT C A. Preparation of Advanced Epoxy Resin by OneStep Procedure

A diglycidyl ether of an adduct of one mole bisphenol A and about 3.4moles (per mole bisphenol A on the average) propylene oxide having anepoxide equivalent weight of 341 g/eq and containing 2.99 wt % totalchlorides (727.0 g, 2.13 eq), bisphenol A (621.8 g, 5.45 eq) and adiglycidyl ether of bisphenol A having an EEW of 188 (1054.8 g, 5.61 eq)are charged to a reactor and heated under nitrogen to 91° C. A 70%solution of ethyltriphenylphosphonium acetate.acetic acid complex inmethanol (5.4 g, 9.22 meq) is added and the mixture is heated to 175° C.and held there for 75 minutes. The product is cooled to below 115° C.and 120.2 g xylene and 762.8 g methylisobutylketone are added. Theepoxide equivalent weight (EEW) at this point is 1029 g/eq, based onnon-volatiles.

B. Preparation of Cationic Resin

The above solution is cooled to 95° C. and diethanolamine at 1 eq/eqepoxide in the reactor (245.3 g, 2.34 eq) is then added and the reactionexothermed to 104° C. The reaction mixture is then maintained at 100° C.for two hours. The product showed 0.794 meq base/g solids at 78.5%solids.

A portion of this amine adduct solution (250 g of solids) is blendedwith 142.9 g of blocked isocyanate crosslinker solution C at ambienttemperature. Propylene glycol phenyl ether (10.5 g), surfactant mixtureA (5.6 g) and acetic acid (0.85 eq/eq base in the amine adduct) are thenadded and mixed. Water is then added dropwise until inversion. Thedispersion is then diluted to 30-35% non-volatiles with water. Themethylisobutylketone and xylene are evaporated out of the aqueousdispersion by stirring two days under a gentle stream of nitrogen.

COMPARATIVE EXPERIMENT D A. Preparation of Advanced Epoxy Resin by Onestep Procedure

A diglycidyl ether of an adduct of one mole bisphenol A and about 6moles (per mole bisphenol A on the average) ethylene oxide having anepoxide equivalent weight of 366 g/eq (292.1 g, 0.798 eq), bisphenol A(225.2 g, 1.98 eq), a diglycidyl ether of bisphenol A having an EEW of188 (382.7 g, 2.04 eq) and 45.0 g xylene are charged to a reactor andheated under nitrogen to 90° C. A 70% solution ofethyltriphenylphosphonium acetate.acetic acid complex in methanol (1.99g, 3.40 meq) is added and the mixture is heated to 175° C. and heldthere for 80 minutes. The product is cooled to below 115° C. and 287.1 gmethylisobutylketone is added. The epoxide equivalent weight (EEW) atthis point is 1062 g/eq, based on non-volatiles.

B. Preparation of Cationic Resin

The above solution is cooled to 92° C. and diethanolamine at 1 eq/eqepoxide in the reactor (86.8 g, 0.827 eq) is then added and the reactionexothermed to 98° C. The reaction mixture is then maintained at 100° C.for two hours. The product showed 0.790 meq base/g solids at 78.9%solids.

A portion of this amine adduct solution (250 g of solids) is blendedwith 142.9 g of blocked isocyanate crosslinker solution C at ambienttemperature. Propylene glycol phenyl ether (10.5 g), surfactant mixtureA (5.6 g) and acetic acid (0.8 eq/eq base in the amine adduct) are thenadded and mixed. Water is then added dropwise until inversion. Thedispersion is then diluted to 30-35% non-volatiles with water. Themethylisobutylketone and xylene are evaporated out of the aqueousdispersion by stirring two days under a gentle stream of nitrogen.

COMPARATIVE EXPERIMENT E A. Preparation of Advanced Epoxy Resin by OneStep Procedure

A diglycidyl ether of an adduct of one mole bisphenol A and about 3.4moles (per mole bisphenol A on the average) propylene oxide having anepoxide equivalent weight of 392 g/eq and containing 145 ppm by weightof total chlorides (225.9 g, 0.576 eq), bisphenol A (157.0 g, 1.38 eq),a diglycidyl ether of bisphenol A having an EEW of 188 (267.1 g, 1.42eq) and 32.5 g xylene are charged to a reactor and heated under nitrogento 94° C. A 70% solution of ethyltriphenylphosphonium acetate.aceticacid complex in methanol (1.40 g, 2.39 meq) is added and the mixture isheated to 175° C. and held there for 195 minutes. The product is cooledto 122° C. and 0.4 g (0.68 meq) of the above phosphonium solution isadded. The reaction mixture is reheated to 175° C. and maintained therefor 81 minutes. The epoxide equivalent weight (EEW) at this point is1057 g/eq, based on non-volatiles. The solution is cooled to 115° C. and207.0 g methylisobutylketone is added. The solution is cooled to ambienttemperature.

B. Preparation of Cationic Resin

The above solution is heated to 90° C. and diethanolamine at 1 eq/eqepoxide in the reactor (62.8 g, 0.598 eq) is then added and the reactionexothermed to 99° C. The reaction mixture, is then maintained at 100° C.for two hours. The product showed 0.829 meq base/g solids at 77.2%solids.

A portion of this amine adduct solution (250 g of solids) is blendedwith 142.9 g of blocked isocyanate crosslinker solution C at ambienttemperature. Propylene glycol phenyl ether (10.5 g), Surfactant MixtureA (5.6 g) and acetic acid (0.8 eq/eq base in the amine adduct) are thenadded and mixed. Water is then added dropwise until inversion. Thedispersion is then diluted to 30-35% non-volatiles with water. Themethylisobutylketone and xylene are evaporated out of the aqueousdispersion by stirring two days under a gentle stream of nitrogen.

EXAMPLE 11

The aqueous resin dispersions from Examples 5-10 and ComparativeExperiments C-E are diluted to 18% non-volatiles and filtered. Thedispersions are then pigmented by adding, with continuous stirring, anappropriate amount of Pigment Dispersion B to yield a pigment-to-binderweight ratio of 0.3, with binder counted as the solids in the resindispersion and pigment vehicle. The pigmented dispersion is stirredovernight, filtered and then used as the coating bath forelectrodeposition. Test panels are coated as described in Example 3. Thepanels are cured at 177° C. for thirty minutes. Results ofelectrodeposition coating of the coating baths made from the examplesand the comparative experiments are summarized in Tables III, IV and V.

Table III shows data for the systems using the 3.4 mole ratio ofpropylene oxide, Table IV for the 6 mole ratio ethylene oxide, and TableV for the low chloride version of the 3.4 mole ratio of propylene oxide.In all cases, materials of the invention using the two-step preparationof the advanced epoxy resin give equal or greater rupture voltage, filmthickness, and/or coulombic efficiency than the comparative experimentsusing the one step preparation of the advanced epoxy resin. This findingis true even for the systems where the dispersion conductivity for thematerials of the invention are higher, a condition for which rupturevoltage and coulombic efficiency normally decline.

                  TABLE III                                                       ______________________________________                                               Coating Designation                                                           A      B       C        D     E*                                       ______________________________________                                        Cationic Ex. 5    Ex. 8   Ex. 9  Ex. 10                                                                              C.E.C.sup.c                            Resin                                                                         Employed                                                                      Dispersion                                                                             1,890    2,130   2,220  2,130 2,010                                  Conductivity.sup.a                                                            Rupture  300      275     275    275   275                                    Voltage                                                                       Coating                                                                       Thickness at                                                                  225 V                                                                         mils     0.44     0.43    0.45   0.48  0.45                                   mm       0.011    0.011   0.011  0.012 0.011                                  Coating                                                                       Thickness at                                                                  250 V                                                                         mils     0.50     0.54    0.57   0.59  0.54                                   mm       0.013    0.014   0.014  0.015 0.014                                  Coulombic                                                                     efficiency.sup.b at                                                           200 volts                                                                               59       48      44     52    43                                    225 volts                                                                               66       51      52     55    49                                    250 volts                                                                               65       55      61     61    55                                    275 volts                                                                               68      --      --     --    --                                     ______________________________________                                         *Not an example of the present invention.                                     .sup.a In micromho/cm; for unpigmented dispersion at 18% nonvolatiles.        .sup.b Expressed as volume cured coating per coulombs measured using          proportional counter ((inches of panel coated × thickness) ÷        proportional amptime count).                                                  .sup.c Comparative Experiment C.                                         

                  TABLE IV                                                        ______________________________________                                                         Coating Designation                                                           A       E*                                                   ______________________________________                                        Cationic Resin Employed                                                                          Ex. 6     C.E.D.sup.c                                      Dispersion Conductivity.sup.a                                                                    1,900     2,090                                            Rupture Voltage    300       275                                              Coating Thickness at 225 V                                                    mils               0.44      0.45                                             mm                 0.011     0.011                                            Coating Thickness at 250 V                                                    mils               0.92      0.81                                             mm                 0.023     0.021                                            Coulombic efficiency.sup.b at                                                 200 volts          61        57                                               225 volts          69        67                                               250 volts          74        69                                               275 volts          80        --                                               ______________________________________                                         *Not an example of the present invention.                                     .sup.a In micromho/cm; for unpigmented dispersion at 18% nonvolatiles.        .sup.b Expressed as volume cured coating per coulombs measured using          proportional counter ((inches of panel coated × thickness) ÷        proportional amptime count).                                                  .sup.c Comparative Experiment D.                                         

                  TABLE V                                                         ______________________________________                                                         Coating Designation                                                           A       E*                                                   ______________________________________                                        Cationic Resin Employed                                                                          Ex. 7     C.E.E.sup.c                                      Dispersion Conductivity.sup.a                                                                    2,140     2,025                                            Rupture Voltage    275       250                                              Coating Thickness at 225 V                                                    mils               0.75      0.63                                             mm                 0.019     0.016                                            Coating Thickness at 250 V                                                    mils               1.10      --                                               mm                 0.028     --                                               Coulombic efficiency.sup.b at                                                 200 volts          60        54                                               225 volts          74        63                                               250 volts          83        --                                               275 volts          --        --                                               ______________________________________                                         *Not an example of the present invention.                                     .sup.a In micromho/cm; for unpigmented dispersion at 18% nonvolatiles.        .sup.b Expressed as volume cured coating per coulombs measured using          proportional counter ((inches of panel coated × thickness) ÷        proportional amptime count).                                                  .sup.c Comparative Experiment E.                                         

What is claimed is:
 1. An advanced epoxy resin composition comprisingthe product resulting from reacting a composition comprising(1) thearomatic hydroxyl-containing product resulting from reacting acomposition comprising(a) at least one diglycidyl ether of (i) anoxyalkylated aromatic diol, or (ii) at least one compound having twohydroxyl groups per molecule in which the hydroxyl groups are attachedto an aliphatic or cycloaliphatic carbon atom and which compound is freeof aromatic rings; or (iii) a combination of (i) and (ii); and (iv)optionally, a diglycidyl ether compound different from (i) and (ii)which is present in an amount such that the amount of epoxy groupscontributed by component (iv) based upon the total amount of epoxygroups contributed by components (i), (ii) and (iv) is from about zeroto about 75 percent; and (b) at least one compound containing twoaromatic hydroxyl groups per molecule; wherein components (a) and (b)are employed in amounts such that there are more aromatic hydroxylgroups present than glycidyl ether groups; (2) at least one diglycidylether of a compound containing two aromatic hydroxyl groups permolecule; (3) optionally, one or more compounds containing two aromatichydroxyl groups per molecule which is different from component (1); and(4) optionally, a monofunctional capping agent; wherein components (1)and (2) are employed in amounts such that the resultant product has anepoxide equivalent weight greater than that of component (2); component(3), when present, is employed in an amount which provides a totalamount of aromatic hydroxyl groups from components (1) and (3) perepoxide group contained in component (2) of from about 0.5:1 to about0.95:1; and component (4), when present, is employed in an amount whichprovides a ratio of epoxy-reactive groups contained in component (4) perglycidyl group not consumed by reaction of components (1) and (3) withcomponent (2) of from about zero: 1 to about 0.7:1.
 2. An advanced epoxyresin of claim 1 wherein(i) component (1a) is one or more compoundsrepresented by the following formula V ##STR13## wherein each R isindependently hydrogen or a hydrocarbyl group having from 1 to 4 carbonatoms; R" is hydrogen or an alkyl group having from 1 to 6 carbon atoms;each m is independently an integer from 1 to 25; n" is 1 or 3; and Z isa divalent aromatic group having from 6 to 20 carbon atoms or Z is agroup represented by the following formulas A, B, C or D: ##STR14##wherein A is a divalent hydrocarbon group having from 1 to 12 carbonatoms, --S--, --S--S--, --SO₂ --, --SO--, --CO--, --O--CO--O--, or--O--; each R is independently hydrogen or a hydrocarbyl group havingfrom 1 to 4 carbon atoms; each R' is independently hydrogen, ahydrocarbyl or hydrocarbyloxy group having from 1 to 4 carbon atoms, ora halogen atom; n has a value of zero or 1; n' has a value from zero to10; and each R^(a) is independently a divalent hydrocarbon group havingfrom 1 to about 6 carbon atoms; (ii) component (1b)is a compoundrepresented by the following formulae III or IV ##STR15## wherein A is adivalent hydrocarbon group having from 1 to 12 carbon atoms, --S--,--S--S--, --SO₂ --, --SO--, --CO--, --O--CO--O--, or --O--; each R isindependently hydrogen or a hydrocarbyl group having from 1 to 4 carbonatoms; each R' is independently hydrogen, a hydrocarbyl orhydrocarbyloxy group having from 1 to 4 carbon atoms, or a halogen atom;n has a value of zero or 1; and n' has a value from zero to 10; (iii)component (2) is a compound represented by the following formulae I orII ##STR16## wherein A is a divalent hydrocarbon group having from 1 to12 carbon atoms, --S--, --S--S--, --SO₂ --, --SO--, --CO--,--O--CO--O--, or --O--; each R is independently hydrogen or ahydrocarbyl group having from 1 to 4 carbon atoms; each R' isindependently hydrogen, a hydrocarbyl or hydrocarbyloxy group havingfrom 1 to 4 carbon atoms, or a halogen atom; n has a value of zero or 1;and n' has a value from zero to 10; (iv) component (3), when present, isa compound represented by the aforementioned formulae III or IV and maybe the same as or different from component (1b); and (v) component (4),when present, is a monofunctional phenol, organic acid or mercaptan. 3.An advanced epoxy resin of claim 1 wherein(i) component (1a) is one ormore compounds represented by the following formula VIII: ##STR17##wherein each R is independently hydrogen or a hydrocarbyl group havingfrom 1 to 4 carbon atoms; R" is hydrogen or an alkyl group having from 1to 6 carbon atoms or a hydrocarbyl; each m is independently an integerfrom zero to about 25; n" has a value of 1 or 3, y has a value of zeroor 1 and Z' is a divalent aliphatic or cycloaliphatic group having from2 to about 20 carbon atoms or Z' is a group represented by the followingformulas A, B, C, D or E: ##STR18## wherein each R' is independentlyhydrogen, a hydrocarbyl or hydrocarbyloxy group having from 1 to 4carbon atoms, or a halogen atom; n has a value of zero or 1; A' andR^(a) are divalent hydrocarbon groups having from 1 to about 6 carbonatoms; R^(b) is hydrogen or a hydrocarbyl group having from 1 to about 6carbon atoms; and x has a value from 2 to about 19; (ii) component(1b)is a compound represented by the following formulae III or IV##STR19## wherein A is a divalent hydrocarbon group having from 1 to 12carbon atoms, --S--, --S--S--, --SO₂ --, --SO--, --CO--, --O--CH--O--,or --O--; each R is independently hydrogen or a hydrocarbyl group havingfrom 1 to 4 carbon atoms; each R' is independently hydrogen, ahydrocarbyl or hydrocarbyloxy group having from 1 to 4 carbon atoms, ora halogen atom; n has a value of zero or 1; and n' has a value from zeroto 10; (iii) component (2) is a compound represented by the followingformulae I or II ##STR20## wherein A is a divalent hydrocarbon grouphaving from 1 to 12 carbon atoms, --S--, --S--S--, --SO₂ --, --SO--,--CO--, --O--CO--O--, or --O--; each R is independently hydrogen or ahydrocarbyl group having from 1 to 4 carbon atoms; each R' isindependently hydrogen, a hydrocarbyl or hydrocarbyloxy group havingfrom 1 to 4 carbon atoms, or halogen atom; n has a value of zero or 1;and n' has a value from zero to 10; (iv) component (3), when present, isa compound represented by the aforementioned formulae III or IV and maybe the same as or different from component (1b); and (v) component (4),when present, is a monofunctional phenol, organic acid or mercaptan. 4.An advanced epoxy resin of claim 2wherein (i) components (1a) and (1b)are employed in amounts which provide a ratio of aromatic hydroxylgroups to epoxy groups of from about 1.05:1 to about 10:1; (ii)components (1) and (2) are employed in amounts which provide a ratio ofaromatic hydroxyl groups to epoxy groups of from about 0.01:1 to about0.95:1; (iii) component (3), when present, is employed in an amountwhich provides a total amount of aromatic hydroxyl groups fromcomponents (1) and (3) per epoxide group contained in component (2) offrom about 0.55:1 to about 0.8:1; and (iv) component (4), when present,is employed in an amount which provides a ratio of epoxy-reactive groupscontained in component (4) per glycidyl group not consumed by reactionof components (1) and (3) with component (2) of from about 0.2:1 toabout 0.5:1.
 5. An advanced epoxy resin of claim 4wherein (i) component(1a) is a diglycidyl ether of the reaction product of bisphenol A,bisphenol F or bisphenol K with propylene oxide in a ratio of from about3 to about 4 moles of propylene oxide per mole of bisphenol; (ii)component (1b) is bisphenol A, bisphenol F or bisphenol K; (iii)component (2) is a diglycidyl ether of bisphenol A, bisphenol F orbisphenol K; (iv) component (3), when present, is bisphenol A, bisphenolF or bisphenol K; (v) component (4), when present, is nonylphenol.